This invention relates to a breather induced lubrication system for the upper valve mechanism of an overhead valve, single cylinder, four stroke, internal combustion engine.
Prior art horizontal crankshaft engines having included breather induced upper valve mechanism lubrication systems wherein the breather was located on top of the rocker box and wherein oil mist was induced to flow upwardly by the breather from the crankcase through both push rod tubes to the rocker box chamber to lubricate the valve actuating mechanism in the rocker box. Oil which condensed in the rocker box was drained back downwardly along the sidewalls of the push rod tubes to the crankcase.
In vertical crankshaft engines the above described breather induced lubrication system does not perform satisfactorily due to several problems. First of all, when the engine is oriented in the head down attitude, oil will not drain from the rocker box to the oil sump thus causing oil to build up in the rocker box. As enough oil builds up the breather will pump oil from the rocker box to the exterior of the engine. This is unsatisfactory because of oil spillage on and around the engine and the loss of lubricating oil which can result in engine failure due to lack of lubrication.
One solution to the above problems is to use a scavenging pump to remove the liquid oil from the rocker box and thereby prevent the build up of liquid oil therein. However, the provision of such a pump adds to the cost of the engine which is unsatisfactory.
Some prior art valve mechanism lubricating structures have been provided whereby liquid oil is pumped from the crankcase through a push rod tube to the valve rocker mechanism whereby the valve rockers operate to splash oil over the moveable members of the rocker arms and bearings. Excess oil is drained out of the rocker chamber through a push rod tube to return to the crankcase. Such systems are unsatisfactory because of the cost of providing the required oil pumping mechanism and furthermore because a separate breather mechanism is required to vent the crankcase.
It is therefore desired to provide a simple, effective valve mechanism lubrication system whereby lubrication is induced by the breather. It is furthermore desired to provide a valve lifter actuation mechanism whereby oil mist in the crankcase is induced by the breather to flow past and thereby lubricate the rocker mechanism, then to be conducted to the breather for venting to the atmosphere, wherein condensed oil is drained back to the oil sump.